Neither. I prefer to not waste space on a heap of dumbbells to pile onto a growing wasteland of unnecessary exercise equipment. Olympic sized dumbbell handles allow one to reuse Olympic barbell plates for loading the weight. The concept is sound in theory, and they are especially good for dumbbell rows, but there's a couple of caveats:
• Standard clamps may or may not work, and it can be really dangerous having plates fall off during a lift, especially if the weight is above you. Mine has screw clamps, and they work okay, but you have to screw it really tight to be secure. You probably want to see and use the dumbbell handle and its clamps in person to know if it will be safe to hold the weight above the body.
• Plates larger in diameter than 25 lb (~11.3 kg) may get in the way by preventing the hands from getting close to the body. 45 lb (~20.4 kg) plates are just ridiculously awkard even if the weight isn’t too heavy. Of course I tried it for laughs once.
I thought this was funny: https://www.youtube.com/watch?v=gRXAs8T7brs These dumbbells seem secure, but it’s a shame they require a special set of plates.
Another example reviewed: https://www.youtube.com/watch?v=A2pP524s_Wc